1,721,060 research outputs found
Coffee ultrafiltration: composition and shelf-life of the permeate
No full textIn this paper, sensory and physio-chemical characteristics of a coffee brew and permeate obtained under iner gas ultrafiltration are described and compared. The coffee permeate, compared to the coffee brew, show a decrease in dry extract content, absence of lipids, a much highter colour and a slight difference in aromas. The coffee permeate is sensorily less bitter and has less richness of flavour than the coffee brew. During shelf-life, the permeate colour is similar to that of the coffee brew. Moreover, sensory evaluation shows that the permeate is much more stable than the coffee brew (weeks for the permeate compared to days for the coffee brew)
Rate of carotenoid degradation in dehydrated carrots
No full textThis work was focused on dehydrated carrots with the aim to study: a) the water sorption properties, and b) the rate of carotenoid degradation as a function of water activity. Freeze-dried carrots from blanched and not blanched batches were placed in air-tight glass jars containing saturated salt solutions with water activity ranging from 0.052 to 0.75, at 40°C. The equilibrium moisture, water activity, and carotenoid content were analysed at different storage times. Results showed that the adsorption isotherm fitted the Guggenheim-Anderson-de-Boer (GAB) equation (R2 = 99.65%). Estimated monolayer water activity was 0.33 (confidential limits at 95%: 0.26 and 0.38). α- and β-Carotene contents decreased in all dehydrated carrots following pseudo-first-order kinetics, with rate constants ranging from 0.031 to 0.374 days-1. Similar rate constants were found between α- and β-carotene. In all carrot batches the rate of carotenoid degradation was at a minimum within the water activity range 0.31 - 0.54. Below and above this range the rate of carotenoid degradation increased significantly. Blanching resulted in a higher initial carotenoid content, but it accelerated carotenoid decrease during storage of dehydrated carrots. Based on these results we concluded that two strategies could be useful to increase carotenoid stability during storage: a) the development of intermediate moisture carrots (water activity in the range 0.31 - 0.54); b) the identification of protective factors that can increase carotenoid stability at water activity above 0.54. Both criteria should be combined with optimised packaging conditions, which reduce exposure of product to air and light during storage
NAIVE MODEL OF STARCH GELATINIZATION KINETICS
No full textA naive model of starch gelatinization kinetics was constructed to determine a control parameter of the baking process (i. e. a baking index). Bread dough samples were instantaneously heated at different temperatures (60-90 degrees C) for varying times and then subjected to differential scanning calorimetry to evaluate the extent of starch gelatinization. Calorimetric traces, after smoothing and standardization, were deconvoluted into one or two Gaussian curves, depending on the treatment temperature and time. This suggests that the system is a mixture of two components, the second of which was found to have lower gelatinization rare.
The kinetic parameterization was only applied to the second Gaussian curve. It was shown that the trend of the second peak fits well with first-order kinetics, where the rate constant varies with temperature according to the Arrhenius equation (K-0 = 2.8 x 10(18)/s; E(a) = 139 kJ/mol)
Effect of water activity on carotenoid degradation in dehydrated carrots
No full textThe effect of water activity on the stability of carotenoids in dehydrated carrots was studied.
Freeze-dried carrots from blanched and unblanched batches were placed in air-tight glass jars containing saturated salt solutions with water activity ranging from 0.052 to 0.75, at 40 C. The equilibrium moisture, water activity, alpha- and beta-carotene, and lutein contents were analysed at different storage times.
The Guggenheim–Anderson–de Boer (GAB) equation was applied to model experimental data for moisture content as a function of water activity, and to calculate the monolayer water activity, where the oxidative reactions are expected to be at minimum. Estimated
monolayer water activity was 0.33 (confidential limits at 95%: 0.26 and 0.38). alpha- and beta-carotene, and lutein degradation followed pseudo-
first-order kinetics in all dehydrated carrots, with rate constants ranging from 0.031 to 0.374 days 1. Similar rate constants were found between alpha- and beta-carotene, whereas lutein degraded faster.
In both blanched and unblanched batches the rate of carotenoid degradation was at a minimum over the water activity range
0.31–0.54. Blanching resulted in a higher initial carotenoid content, but it accelerated carotenoid decrease during storage of dehydrated
carrots
La gestione dell'autocontrollo igienico nelle imprese agro-alimentari. Il comparto delle carni trasformate
No full textPredictive study on Tuscan extra virgin olive oil stability under several commercial conditions
No full textIndustries aim to ensure extra virgin olive oil (EVOO) stability especially during commercial activities up to use by end consumers. The objective of this work was to set up predictive models of EVOO stability during commercial activities. Stability was studied on five lots of a batch of Tuscan virgin olive oil to simulate different commercial activities. Chemical, physical, and sensory analyses were carried out on EVOO samples. Experimental data were processed by multivariate analyses to select significant parameters and by regression analyses to set up kinetic models. A few parameters were found to be significant: hydroxytyrosol and tyrosol contents, carotenoid absorbance at 475 and 448 nm, α-tocopherol content, Rancimat induction time, and K232. It was also shown that the stability of this EVOO was not significantly influenced by different uncontrolled bottling, transport, and storage conditions in supermarkets. Empirical models were set up to predict the time to reach a reference value for K232
Studio della conservabilità di spremute di arancia fresche da agricoltura biologica (Shelf-life of freshly squeezed orange juice from organic farming methods)
No full textStudy of the stability of dried tomato halves during shelf-life to minimise oxidative damage
Get PDFOptimal operating conditions for storage of dried tomato halves were investigated to obtain decreased oxidative damage, evaluated in terms of colour variation, combined with microbial stability of the product, ie inhibition of growth of eumycetes. Experiments were planned using a saturated factorial design. Variables studied were the moisture content of dried tomato halves in the range 10-60%, temperature in the range 5-30 degreesC and storage time in the range 1-38 days. Eighteen storage experiments were carried out in the dark under vacuum at the storage conditions indicated by the experimental design. At the end of each experiment, surface colour was measured by a tristimulus colorimeter, and growth of eumycetes was evidenced by olfactory and visual perception, followed by qualitative microbial analysis. Eumycetes were present in all stored products, except that at 10% moisture, and, generally speaking, storage conditions did not allow micro-organisms to grow. From isoresponse curves the optimal region for storage to minimise oxidative damage was extrapolated, which was represented by residual moisture values between 20 and 40% and less than or equal to 18 degreesC storage temperature, with a minimum point of colour variation at approximately 30% moisture content and 10 degreesC
Water sorption, drying and antioxidant properties of dried tomato products
No full textThis work is focused on some properties of various dried tomato products (tomato pulp, tomato halves and insoluble solids-rich tomato), useful to optimize drying processes. Adsorption and desorption isotherms at 20 C of these products were measured and modelled by the Guggenheim–Anderson–de Boer (GAB) equation. Insoluble solids-rich tomato was the least hygroscopic of all tomato products. Tomato products were air-dried in a pilot plant and the drying kinetics was modelled. The mass transfer equation
for drying of thin slabs, modified to include shrinkage of samples during drying, was successfully applied to experimental data.
Apparent water diffusivity values ranged from 2:3 10 9 to 9:1 10 9 m2/s as a function of the structure of tomato products. The lycopene and ascorbic content and the antioxidant activity of hydrophilic and lipophilic extracts were measured both on fresh and dried tomato products. Interesting properties of insoluble solids-rich tomato were evidenced: it had the highest lycopene content (ca. 12,000 mg/kg dm) and lipophilic antioxidant activity (ca. 400I50; lg dm) of all tomato products. 2002 Elsevier Science Ltd. All
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